(P-CB-17) In Vitro Feasibility of Cold Stored Platelets at Elevated Concentrations

Background/Case Studies: Platelets are traditionally stored at room temperature to maintain their viability and function. However, storage at cold temperatures (1–6 °C) has been shown to slow platelet metabolism, reduce bacterial proliferation risk, and extend shelf life for select indications. Optimizing high concentration storage could reduce the volume of plasma or additive solution required and improve storage efficiency.

Study

Design/Methods: Hyperconcentrated platelets (N=3) were collected at a target yield of approximately 6x10¹¹ platelets (Amicus Separator). All subsequent processing was performed aseptically. Each apheresis product was subdivided into three small-volume polyolefin containers, targeting a Control concentration of 1500x10³ PLT/µL, and Test conditions 2 and 5 times this amount (Test-2x, Test-5x, respectively). Target storage fluid volume (65% InterSol/35% autologous plasma) was approximately 40 mL for all conditions. Day 0 sampling was conducted, and products were placed in cold storage for 21 days with sampling every 7 days. In vitro parameters assessed included: platelet (PLT) counts, pH, lactate dehydrogenase (LDH), thromboelastography (TEG), platelet activation (CD62), glucose, lactate, and morphology (Kunicki score). Control data was compared with test conditions by paired t-test for initial assessment of data trends.

Results/Findings: Pre-storage platelet concentrations (x10³/µL) achieved were as follows: 1531±140 (Control), 3147±224 (2x-Test), 8023±609 (5x-Test). Day 21 data is presented in Table 1. All units maintained pH above 6.2. Lactate produced per platelet (mmol/10¹² PLT) decreased with increasing platelet concentration, possibly due to more rapid glucose depletion at higher concentrations or intrinsic metabolic differences between conditions. Supernatant LDH increased with increasing platelet concentration and storage duration. When normalized to platelet count, LDH released during storage was lowest for the 2x-Test condition (calculated two ways: normalized to platelet count and as a percentage of Total LDH measured). TEG results showed lower clot strength (MA) for the 5x platelet concentration, while at 2x concentration, results were similar to the Control. Activation (CD62) was comparable between Control and Test conditions throughout storage. Morphology scores trended lower in Test groups, with more microaggregates and damaged cell types observed in the 5x-Test condition.

Conclusions: This preliminary study suggests that cold storage of platelets at up to twice the standard concentration may be feasible, although more data is needed to better understand the impact on cell integrity and metabolism for higher concentration conditions. Additional studies are warranted to further characterize these parameters for cold stored, high concentration platelets and to assess whether increased PAS fractions could enable further plasma conservation without compromising product quality.